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The morphodynamics of a swash event on an erodible beach

Published online by Cambridge University Press:  02 December 2014

Fangfang Zhu  and
Nicholas Dodd
Fangfang Zhu*
Affiliation:
Department of Civil Engineering, University of Nottingham, Taikang East Road, Ningbo 315100, China
Nicholas Dodd
Affiliation:
Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK
*
†Email address for correspondence: Fangfang.Zhu@nottingham.edu.cn
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Abstract

A high-accuracy numerical solution, coupling one-dimensional shallow water and bed-evolution equations, with, for the first time, a suspended sediment advection equation, thereby including bed and/or suspended load, is used to examine two swash events on an initially plane erodible beach: the event of Peregrine & Williams (J. Fluid Mech., vol. 440, 2001, pp. 391–399) and that of a solitary wave approaching the beach. Equations are solved by the method of characteristics, and the numerical model is verified. Full coupling of suspended load to beach change for Peregrine & Williams (J. Fluid Mech., vol. 440, 2001, pp. 391–399) yields only slightly altered swash flows, depending on beach mobility and sediment response time; a series of similar final beach change patterns results for different beach mobilities. Suspended- and bed-load transport have distinct morphodynamical signatures. For the solitary wave a backwash bore is created (Hibberd & Peregrine, J. Fluid Mech., vol. 95, 1979, pp. 323–345). This morphodynamical bore propagates offshore initially, and leads to the creation of a beach bed step (Larson & Sunamura, J. Sedimentary Petrology, vol. 63, 1993, pp. 495–500), primarily due to bed-load transport. Its height is directly related to bed-load mobility, and also depends strongly on the bed friction coefficient. The shock dynamics of this bed step is explained and illustrated. Bed- and suspended-load mobilities are quantified using field data, and an attempt is made to relate predictions to measurements of single swash events on a natural beach. Average predicted bed change magnitudes across the swash are of the order of 2 mm, with maximum bed changes of up to approximately 10 cm at the bed step.

JFM classification

Geophysical and Geological Flows: Coastal engineering Geophysical and Geological Flows: Sediment transport Geophysical and Geological Flows: Shallow water flows
Type
Papers
Information
Journal of Fluid Mechanics , Volume 762 , 10 January 2015 , pp. 110 - 140
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Copyright
© 2014 Cambridge University Press 

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References

Antuono, M. & Hogg, A. J. 2009 Run-up and backwash bore formation from dam-break flow on an inclined plane. J. Fluid Mech. 640, 151–164.Google Scholar
Antuono, M., Soldini, L. & Brocchini, M. 2012 On the role of the Chezy frictional term near the shoreline. Theor. Comput. Fluid Dyn. 26, 105–116.CrossRefGoogle Scholar
Barnes, M. P., O’Donoghue, T., Alsina, J. M. & Baldock, T. E. 2009 Direct bed shear stress measurements in bore-driven swash. Coast. Eng. 56, 853–867.Google Scholar
Blenkinsopp, C. E., Turner, I. L., Masselink, G. & Russell, P. E. 2011 Swash zone sediment fluxes: field observations. Coast. Eng. 58, 28–44.Google Scholar
Briganti, R., Dodd, N., Pokrajac, D. & O’Donoghue, T. 2011 Nonlinear shallow water modelling of bore-driven swash: description of the bottom boundary layer. Coast. Eng. 58 (6), 463–477.Google Scholar
Butt, T. & Russell, P. 2005 Observations of hydraulic jumps in high-energy swash. J. Coast. Res. 16 (6), 1219–1227.Google Scholar
Butt, T., Russell, P., Puleo, J. & Masselink, G. 2005 The application of Bagnold-type sediment transport models in the swash zone. J. Coast. Res. 21 (5), 887–895.CrossRefGoogle Scholar
Guard, P. A. & Baldock, T. E. 2007 The influence of seaward boundary conditions on swash zone hydrodynamics. Coast. Eng. 54, 321–331.CrossRefGoogle Scholar
Hibberd, S. & Peregrine, D. H. 1979 Surf and run-up on a beach: a uniform bore. J. Fluid Mech. 95, 323–345.Google Scholar
Horn, D. P. & Mason, T. 1994 Swash zone sediment transport modes. Mar. Geol. 120, 309–325.Google Scholar
Hughes, M. G., Masselink, G. & Brander, R. W. 1997 Flow velocity and sediment transport in the swash zone of a steep beach. Mar. Geol. 138, 91–103.Google Scholar
Jeffrey, A. 1976 Quasilinear Hyperbolic Systems and Waves. Pitman.Google Scholar
Kelly, D. M. & Dodd, N. 2009 Floating grid characteristics method for unsteady flow over a mobile bed. Comput. & Fluids 38, 899–909.CrossRefGoogle Scholar
Kelly, D. M. & Dodd, N. 2010 Beach face evolution in the swash zone. J. Fluid Mech. 661, 316–340.CrossRefGoogle Scholar
Larson, M. & Sunamura, T. 1993 Laboratory experiment on flow characteristics at a beach step. J. Sedimentary Petrology 63 (3), 495–500.Google Scholar
Masselink, G., Austin, M., Tinker, J., O’Hare, T. & Russell, P. 2008 Cross-shore sediment transport and morphological response on a macrotidal beach with intertidal bar morphology, Truc vert, France. Mar. Geol. 251, 141–155.CrossRefGoogle Scholar
Masselink, G., Evans, D., Hughes, M. G. & Russell, P. 2005 Suspended sediment transport in the swash zone of a dissipative beach. Mar. Geol. 216, 169–189.Google Scholar
Masselink, G. & Hughes, M. 1998 Field investigation of sediment transport in the swash zone. Cont. Shelf Res. 18, 1179–1199.Google Scholar
Masselink, G. & Hughes, M. G. 2003 Introduction to Coastal processes & Geomorphology. Hodder Arnold.Google Scholar
Masselink, G., Russell, P., Blenkinsopp, C. & Turner, I. 2010 Swash zone sediment transport, step dynamics and morphological response on a gravel beach. Mar. Geol. 274, 50–68.Google Scholar
Mei, C. C. 1990 The Applied Dynamics of Ocean Surface Waves. Advanced Series on Ocean Engineering, vol. 1, 2nd edn. World Scientific.Google Scholar
Peregrine, D. H. & Williams, S. M. 2001 Swash overtopping a truncated beach. J. Fluid Mech. 440, 391–399.Google Scholar
Pritchard, D. 2009 Sediment transport under a swash event: the effect of boundary conditions. Coast. Eng. 56, 970–981.CrossRefGoogle Scholar
Pritchard, D. & Hogg, A. J. 2003 Cross-shore sediment transport and the equilibrium morphology of mudflats under tidal currents. J. Geophys. Res. 108 (C10), 3313.Google Scholar
Pritchard, D. & Hogg, A. J. 2005 On the transport of suspended sediment by a swash event on a plane beach. Coast. Eng. 52, 1–23.CrossRefGoogle Scholar
Pritchard, D. & Hogg, A. J. 2006 Reply to discussion of On the transport of suspended sediment by a swash event on a plane beach [Coast. Eng. 52, (2005), 1–23]. Coast. Eng. 53, 115–118.Google Scholar
Shen, M. C. & Meyer, R. E. 1963 Climb of a bore on a beach. Part 3. Run-up. J. Fluid Mech. 16, 113–125.Google Scholar
Soulsby, R. L. 1997 Dynamics of Marine Sands. Thomas Telford.Google Scholar
Van Rijn, L. C. 1993 Principles of Sediment Transport in Rivers, Estuaries and Coastal Seas. Part 1. Aqua Publications.Google Scholar
Van Rijn, L. C. 2006 Principles of Sediment Transport in Rivers, Estuaries and Coastal Seas. Part 2. Aqua Publications.Google Scholar
Yalin, M.S. 1977 Mechanics of Sediment Transport, 2nd edn. Pergamon.Google Scholar
Zhu, F. & Dodd, N. 2013 Net beach change in the swash: A numerical investigation. Adv. Water Resour. 53, 12–22.CrossRefGoogle Scholar
Zhu, F., Dodd, N. & Briganti, R. 2012 Impact of a uniform bore on an erodible beach. Coast. Eng. 60, 326–333.CrossRefGoogle Scholar